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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef BASE_FILES_DIR_READER_LINUX_H_
6 #define BASE_FILES_DIR_READER_LINUX_H_
7 
8 #include <errno.h>
9 #include <fcntl.h>
10 #include <stddef.h>
11 #include <stdint.h>
12 #include <sys/syscall.h>
13 #include <unistd.h>
14 
15 #include "base/logging.h"
16 #include "base/macros.h"
17 #include "base/posix/eintr_wrapper.h"
18 
19 // See the comments in dir_reader_posix.h about this.
20 
21 namespace base {
22 
23 struct linux_dirent {
24   uint64_t        d_ino;
25   int64_t         d_off;
26   unsigned short  d_reclen;
27   unsigned char   d_type;
28   char            d_name[0];
29 };
30 
31 class DirReaderLinux {
32  public:
DirReaderLinux(const char * directory_path)33   explicit DirReaderLinux(const char* directory_path)
34       : fd_(open(directory_path, O_RDONLY | O_DIRECTORY)),
35         offset_(0),
36         size_(0) {
37     memset(buf_, 0, sizeof(buf_));
38   }
39 
~DirReaderLinux()40   ~DirReaderLinux() {
41     if (fd_ >= 0) {
42       if (IGNORE_EINTR(close(fd_)))
43         RAW_LOG(ERROR, "Failed to close directory handle");
44     }
45   }
46 
IsValid()47   bool IsValid() const {
48     return fd_ >= 0;
49   }
50 
51   // Move to the next entry returning false if the iteration is complete.
Next()52   bool Next() {
53     if (size_) {
54       linux_dirent* dirent = reinterpret_cast<linux_dirent*>(&buf_[offset_]);
55       offset_ += dirent->d_reclen;
56     }
57 
58     if (offset_ != size_)
59       return true;
60 
61     const int r = syscall(__NR_getdents64, fd_, buf_, sizeof(buf_));
62     if (r == 0)
63       return false;
64     if (r == -1) {
65       DPLOG(FATAL) << "getdents64 returned an error: " << errno;
66       return false;
67     }
68     size_ = r;
69     offset_ = 0;
70     return true;
71   }
72 
name()73   const char* name() const {
74     if (!size_)
75       return nullptr;
76 
77     const linux_dirent* dirent =
78         reinterpret_cast<const linux_dirent*>(&buf_[offset_]);
79     return dirent->d_name;
80   }
81 
fd()82   int fd() const {
83     return fd_;
84   }
85 
IsFallback()86   static bool IsFallback() {
87     return false;
88   }
89 
90  private:
91   const int fd_;
92   alignas(linux_dirent) unsigned char buf_[512];
93   size_t offset_;
94   size_t size_;
95 
96   DISALLOW_COPY_AND_ASSIGN(DirReaderLinux);
97 };
98 
99 }  // namespace base
100 
101 #endif  // BASE_FILES_DIR_READER_LINUX_H_
102